Industrial Crops & Products 128 (2019) 496–503 Contents lists available at ScienceDirect Industrial Crops & Products journal homepage: www.elsevier.com/locate/indcrop Chemical features and bioactivities of cornflower (Centaurea cyanus L.) T capitula: The blue flowers and the unexplored non-edible part Lara Lockowandta,b, José Pinelaa, Custódio Lobo Roriza, Carla Pereiraa, Rui M.V. Abreua, ⁎ Ricardo C. Calhelhaa, Maria José Alvesa, Lillian Barrosa, Michael Bredolb, Isabel C.F.R. Ferreiraa, a Centro de Investigação de Montanha (CIMO), Instituto Politécnico de Bragança, Campus de Santa Apolónia, 5300-253, Bragança, Portugal b Münster University of Applied Sciences, Department of Chemical Engineering, Stegerwaldstr. 39, 48-565, Steinfurt, Germany ARTICLE INFO ABSTRACT Keywords: Cornflower is a flowering weed and ornamental plant whose blue flowers have been used for food,decorative Centaurea cyanus L. and colouring purposes. In this study, the upper (edible flowers) and lower (non-edible receptacle and involucre) Cornflower capitula parts of the capitulum were studied and compared for their chemical composition and bioactive properties. The Phenolic compounds flowers were richer in tocopherols, organic acids, and apigenin derivatives (mainly apigenin-7-O-glucuronide-4′- Anthocyanins O-(6-O-malonylglucoside)) than the non-edible bristly part (where syringic acid predominated). Four cyanidin Antioxidant activity derivatives were identified in the flowers. The extract of the non-edible part was more efficient ininhibitingthe Antibacterial activity formation of thiobarbituric acid reactive substances (TBARS), the bleaching of β-carotene, and the haemolysis of the erythrocytes membrane. In general, the extracts were more active against Gram-positive bacteria and had no cytotoxicity against non-tumour liver PLP2 cells. Therefore, while flowers are a potential source of natural cyanidin-based colorants, the lower part of the capitulum has bioactive properties to be exploited in different food or pharmaceutical formulations. 1. Introduction a counterpart towards the production of reactive oxygen species (ROS) (Martins et al., 2016). The human body produces ROS through normal Centaurea cyanus L. (syn. Cyanus segetum Hill) is an annual metabolism. They can show an effective defence against infections and Asteraceae species that grows in many countries throughout Europe take part in cellular signalling pathways. However, once an over- and Asia (Hellwig, 2004). This flowering weed is commonly known as production of these reactive species occurs, the effects become detri- “cornflower” or “bachelors button” and often noticeable next to corn- mental as they attack free lipids and DNA (Valko et al., 2007). Next to fields due to an intensive blue colour provided by a supramolecular the fact that the accumulation of DNA damage has shown to be one of pigment called protocyanin (Kondo et al., 1998). This pigment is in fact the major reasons for aging, the influence of ROS on the normal cell a metalloanthocyanin-complex formed by an anthocyanin, a flavone, functioning is responsible for many degenerative diseases like cardio- Fe3+ and Mg2+ in the stoichiometric order 6:6:1:1. The anthocyanin in vascular disease, diabetes, and different types of cancer (Reuter et al., the complex has been identified as cyanidin-3-O-(6-O-succinylgluco- 2010). Since free radicals are not only generated by normal metabolic side)-5-O-glucoside, while apigenin-7-O-glucuronide-4′-O-(6-O-mal- process, but also through external factors like pollution, radiation or onylglucoside) is the corresponding flavone (Kondo et al., 1998; smoking, it quickly comes to an overproduction and so called oxidative Takeda, 2006). These molecules are bound through metal complexation stress (Reuter et al., 2010). as well as hydrophobic interactions regarding anthocyanins and fla- Facing this challenge, a diet that includes foods and supplements vones. Since these bonds are quite weak, the protocyanin only exhibits with antioxidant activity can function as a preventive medicine (Pinela a very stable blue colour in concentrated solutions; as soon as it is di- et al., 2012b). One of the propagating factors for an enhanced research luted, the colour fades (Yoshida et al., 2009). in this field was the so-called “French paradox”, which showed that Anthocyanins and flavones are phenolic compounds with hydrogen- people with a moderate red-wine consumption wouldn’t suffer from donating properties through one of the hydroxyl-groups. This makes heart disease despite a fat based diet (Renaud and de Lorgeril, 1992). them compounds with a high antioxidant potential, capable of acting as Results of this investigation led to anthocyanins and other polyphenols ⁎ Corresponding author. E-mail address: [email protected] (I.C.F.R. Ferreira). https://doi.org/10.1016/j.indcrop.2018.11.059 Received 10 August 2018; Received in revised form 9 November 2018; Accepted 12 November 2018 Available online 27 November 2018 0926-6690/ © 2018 Elsevier B.V. All rights reserved. L. Lockowandt et al. Industrial Crops & Products 128 (2019) 496–503 as strong bioactive compounds. Due to this fact and also to the col- Japan) and expressed in g per 100 g of plant dry weight (dw). ouring capacity, anthocyanins are already used as natural colorants with health promoting capacity in foodstuff (Roriz et al., 2018). But it’s not only in this sector that the interest for natural colorants and 2.3. Analysis of tocopherols bioactives is growing. Health awareness and lifestyle of today's society are changing towards an earlier lifestyle with a focus on natural pro- Tocopherols were determined following a procedure previously ducts (Pires et al., 2018; Rop et al., 2012). described by Barros et al. (2013), using a HPLC system (Knauer, The present study faces a detailed characterisation of the cornflower Smartline system 1000, Berlin, Germany) coupled to a fluorescence capitula. While the blue flowers find a great interest as a potential detector (FP-2020; Jasco, Easton, MD, USA) programmed for excitation source of natural colouring agents, as well as in food preparation de- at 290 nm and emission at 330 nm, and the internal standard (tocol, riving for example from an increasing popularity in garnishing dishes Matreya, Pleasant Gap, PA, USA) method for quantification. Chroma- (Pires et al., 2018; Rop et al., 2012), the receptacle and involucre (non- tographic separation was performed in normal-phase with a Polyamide edible bristly part) is a unexplored by-product of no commercial value. II column (5 μm particle size, 250 × 4.6 mm; YMC, Kyoto, Japan). However, it may be an interesting source of bioactive compounds to be Elution was performed with a mixture of n-hexane and ethyl acetate used in the development of functional foods, nutraceuticals, or phar- (70:30, v/v; HPLC grade, Lab-Scan, Lisbon, Portugal). The results were maceutical formulations. For that matter, the blue flowers were ana- recorded and processed using Clarity 2.4 software (DataApex, Prague, lysed separately from the non-edible lower part of the capitulum. Czech Republic) and expressed in mg per 100 g of plant dry weight Until now some studies have been performed to characterize the (dw). flower pigments. A good summary about the historical development in research about the blue flower colour is presented by Yoshida et al. (2009). Reports regarding the evaluation of the bioactive potential of 2.4. Preparation of hydromethanolic extracts flower or capitulum extracts also exist from different authors(Escher et al., 2018; Garbacki et al., 1999; Marian et al., 2017; Pires et al., The powdered samples (∼1 g) were subjected to a solid-liquid ex- 2018). However, as far as we know, no studies describing the bioactive traction with a methanol/water mixture (80:20, v/v; 30 mL). Acidified potential of the non-edible receptacle and involucre separately from the solvent (0.05% trifluoroacetic acid) was used for the flower samples. flowers exist in the literature. Therefore, this study was performed to The extraction was performed at 25 °C and 150 rpm during 1 h, fol- characterize and compare the profiles in organic acids, tocopherols and lowed by filtration through filter paper (Whatman No. 4). Afterwards, phenolic compounds, including anthocyanins, of the blue flowers and the extraction procedure was repeated with the residue. In case of the non-edible lower part of the cornflower capitula, as well as to evaluate flower sample, the extraction was repeated up to five times untilthe the antioxidant, antihaemolytic, anti-proliferative and antimicrobial residue lost all colour. The combined extracts were then concentrated properties of these plant parts. under reduced pressure at 40 °C (rotary evaporator Büchi R-210, Flawil, Switzerland) and the aqueous phase was lyophilised. The dried extracts 2. Material and methods were kept in the best conditions until further analysis. 2.1. Plant samples 2.5. Analysis of phenolic compounds Fresh cornflower samples were purchased from “Blumen Lennartz”, a flower shop in Münster, Germany. The tubular blue flowers (edible The dried extracts were re-dissolved in water/methanol (80:20, v/v) part) of the capitulum (or flower head) were first separated from the at 10 mg/mL and filtered through a 0.22-μm disposable LC filter disk. non-edible part corresponding to the bristly receptacle and imbricated The analysis was performed by high performance liquid chromato- involucre, and separately processed. Then, both samples were lyophi- graphy coupled to a diode array